1) Somehow the firmware link has been put on another page than the "firmware" page of the website, a bit confusing.
2) The "Firmware Update" link to the manual on the separate DM42 page (https://www.swissmicros.com/dm42/firmware/) is wrong.
3) The procedure given in the manual is apparently not correct:
I had to eject, but also to press EXIT on the DM42 once it was unmounted, and confirm, there was no detection at all from the calculator. (using Win7 x64 Pro)Activate USB disk from DM42 program "SETUP → Files → Activate USB Disk" or directly from DMCP System menu.
Connect USB cable from DM42 to PC/Mac computer.
Copy the DMCP_flash_x.x_DM42-y.y.bin file from the PC/Mac computer to root folder of calculator disk.
Eject (safely remove) the calculator disk from PC/Mac computer. Please, be patient this can take some time. Don’t unplug USB cable until safely ejected from OS.
Calculator detects presence of new firmware file and asks for update. You can confirm it immediately or press EXIT key and activate flashing process later using "Flash firmware from FAT" either from DM42 program "SETUP → System" or directly from DMCP System menu "Enter System Menu"
Once finished the calculator resets and should restart to updated DM42 program.
By the way, be careful when pressing EXIT to stop the USB disk on the calculator side. After pressing that key you have to confirm with the ENTER key, and because of the very annoying key bouncing problem of the DM42, it may register twice ... and the next menu proposes the firmware update. It happened to me once, and I lost all my content because of that